Atomic Structure

Hey everyone. So we're calling from general chemistry that the atom is the basic unit of matter and a collection of atoms is what helps to make a molecule. Now talking about adam we have an example of an atom in the top right corner here. Remember at the center of an atom is where we have a majority of the mass of the atom. That's where we have our protons and our neutrons here is not drawn to scale. The nucleus is very small here. We're just zooming in on it. So we can see the protons and the neutrons also remember that zooming around this are electrons which are found within different orbits. Now also remember that the atomic number of an atom is equal to the number of what That's right. Number of protons also remember that the atomic number is unique to a given element. So an element has atomic number and only that element has that atomic number. Besides the atomic number, we have the mass number. The mass number of an atom is equal to the number of protons plus neutrons. So we're talking about the total number of the subatomic particles with the nucleus of a particular atom. With this whole idea of protons, neutrons and electrons. We also know another term isotopes now, isotopes. These are a type of element that have the same number of protons and therefore the same atomic number but they have deferring neutrons. So their mass numbers is what's different from them. So they all have the same number of protons that it's just their mass numbers that are different. We'll go into further explanations for what exactly is an isotope and some examples in the following video.

Hey everyone. So here we're gonna take a look at hydrogen isotopes. Now, before we begin first realize that an isotope is not a new type of atom, all it is is a heavier form of the same atom and we make it heavier by adding neutrons here we have hydrogen deuterium and tritium for each of them. They all are just this all hydrogen, you're just in different forms because all of them have an atomic number of one. Remember the bottom number here represents our atomic number, the number of protons, a number of top we're going to say that represents our mass number, which remember is the number of protons plus neutrons. So if we take a look here at the first one, which is just regular hydrogen, it has an atomic number of one. So it has one proton and its mass number is also one. If we were to subtract those two numbers, that will give us the number of neutrons. So we'd say here that hydrogen regular hydrogen has one proton and zero neutrons. Next we add one neutron. And when we do that, we create deuterium, deuterium is going to be an isotope of hydrogen. You're going to see later on throughout organic organic chemistry, you won't find it on the periodic table. You'll just see hydrogen there. Remember deuterium is just another form of the hydrogen atom, It's gotten heavier by adding an additional neutron here, we abbreviate it as deep here, we'd say that since its atomic number is still one, it still has one proton. So It's still one p plus. And then if we subtract those two numbers from each other to -1, we get one which is the number of neutrons. Then what we can do is you can add another neutron and that would help to create. Iridium. Iridium is abbreviated as just t. Again, you wouldn't find this on the periodic table. This is just another form of the hydrogen atom. Here we have one proton still and then two neutrons. So you can see that all of them are hydrogen because all of them have one proton. But they're all different forms of hydrogen because they have different number of neutrons. Also realize that adding neutrons comes at a cost. If you're adding more neutrons to create different isotopes, you're gonna affect the stability of your atom. It's gonna become less stable. So here trillium is incredibly unstable. Doesn't last but for a few moments because we're adding too many neutrons also remember that besides stability, we also talked about scarcity. So here hydrogen before we've added any neutrons is the most stable of these three. So a majority of hydrogen is found in this form as we go towards treaty. Um the percentage of hydrogen existing in that form goes lower and lower. Alright, so just remember that isotopes are just different forms of the same atom, they're just heavier forms of that atom. And we do that by adding neutrons

now we're gonna talk a little bit about just atomic structure. Okay, so remember that electrons orbit regions around a nucleus. Okay. And they orbit it based on energy level. Okay, so that region of space that has a certain energy is called a shell. Okay, a shell is that space that a certain energy where the electrons can can move. Alright, now, shells remember shells can hold a lot of electrons. Some shells can hold up to 18 electrons, something like that. But there's a smaller subset of space within a shell that holds exactly enough. That has enough room for exactly one pair of electrons. Do you remember what that is called? That would be called an orbital? Okay. An orbital. Is that region of space that only two electrons and up spin and a down spin can exist in? Okay, we're gonna talk a lot about orbital's later. All right then. What happens when we already talked about what happens when Adams have different amounts of neutrons? All right. But when Adams possessed a different number of electrons than protons. So now we're talking about what happens if they have different amounts of electrons. What's gonna happen is that instead of being heavier or lighter, electrons don't really contribute to mass very much. Remember that electrons are tiny, tiny, tiny. They do not they're not very heavy. Instead they're gonna contribute towards the charge. So, these are called ions. Okay, remember the word ion just describe something that is a charged atom. Alright, so, remember there's two kinds of charges. You could have you could have a positive or a negative. You guys should be able to fill this in. What is it called when it's a positively charged atom? That's a cat iron. Okay. Please don't say cash in. Okay, that is not a cash in. That is a cat ion. Alright. A negatively charged would be called an an ion. Okay, so it's important that you guys know this distinction basically different amounts of neutrons actually affects the weight. So you get a different atomic mass. Different amounts of electrons doesn't affect the weight that much, but it does affect the charge. Why? Because if you think about it, electrons have a negative charge. Protons have a positive charge in atoms. These are supposed to perfectly balance out. You're supposed to have exactly as many protons as you have electrons. If you have a difference then you're gonna have a net charge for that. All right.

So here's an example of some really good ions right here. So these are the simplest form of ions you can make, which would be the positive hydrogen and the negative ion of hydrogen. So let's talk about the positive one. Normally a hydrogen atom is a proton and an electron. If I take away one of those electrons, what's going to wind up happening is that I'm going to get a positive charge. Okay, I'm going to get a positively charged adam. And the reason is because I have nothing to counteract the positive charge of the of the, of the proton. All right now, when you have one of these H plus ions, it's actually just called a proton. Why? Because there's nothing else. There's no neutrons, there's no electrons. So literally we just call it protons. So when I say, hey, there's a proton whizzing whizzing around. That means it's a hydrogen that does not have an electron on it. Okay. And that means it has a positive charge. Then a hydride is the name of hydrogen that has a negative charge. Now, why would hydrogen ever have a negative charge? Well, if it has more than one electron for example, it has two electrons, then the electrons are gonna win. There's only more electrons and protons. So you have a net negative. So h minus is hydride H plus is a proton and you guys need to know that that's actually super important for organic chemistry

So now, finally what I want to talk about is the three principles of electronic configuration. We're gonna do some practice with this later. But these principles you learn in gen, can you just need to commit them to memory? Okay, you're still gonna need them for or go. So what these do is they describe the way that electrons fill atomic orbital's. Remember that orbital's hold two electrons? The aft about principle is also called the building up principal building but Okay, and with the building up principle, what happens is that it just says, hey, if you have orbital's of differing energies, you have to fill the lowest energy first. Okay, so remember that we're gonna talk more about this later, but remember that the one s orbital is your lowest energy orbital and then it goes up to two S and then it goes to two P and then you get they start going into the into the DS and FS and everything. Okay, so that means you wouldn't fill a f orbital or a D orbital before you completely filled all your lower orbital's. Alright, so you always have to start at the bottom and work your way up. Easy then you have the Pauli exclusion principle. This one. You guys already know all it says is that you can only have two electrons per orbital. So I already told you this, but you didn't know that it was Pauli exclusion. Maybe you forgot. Okay, um or maybe you remembered, Sorry, you could have totally remembered that. I just assume I teach this class, like as if you don't remember anything from gen cam. So the way that I like to think about it, is that imagine these two electrons are like out on a date. Okay. And then, like someone tries to join in and it's like a third wheel, they're gonna be exclusive, they're gonna be like, no, like go away, like, I want to be on a date. Right? So, Pauli exclusion, they're like, excluding the other electrons. Alright, so it's Pauli exclusion then finally, ever last one, which is huns rule, Hunt's rule can be compared to a lot of people compared to like you're on a school bus and it's like the seats of a bus. Alright, so basically you have a certain amount of kids and you know, well, I don't know, kids are weird, but if you had a normal bus, a normal like bus with adults, what happened is that people always take the clear seats first, No one doubles up on a seat for no reason, they always take all the clear seats. And once all the seats have one person on them, then you start putting your second people. Okay, And basically that's what Hunt's rule says, it says that you have to evenly fill all of your orbital of the same energy level before you can start adding second electrons to those. Alright, so in this case, just remember that you're gonna, anything that has equal energy, you're gonna equally fill it with one electron first and then you can start adding second ones. Alright, so guys, it's just important that you guys remember what these rules are about and we're gonna apply it in some practice problems. You guys will get some practice. Alright, so let's go on and try it out.